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CTSW FUEL TANKS

I recently had the wings removed from my CTSW for inspection. I'd told the guys doing the work that there would be 60-70L fuel in the tanks. They called me to let me know that when they drained it, it all went into two 20L cans and they estimated about 35L. I was very surprised as I never run it this low due to the issues discussed above, so took more fuel with me when I went to collect it. As soon as I saw the level in the sight tubes I knew that the dipstick reading would be higher than 35. Sure enough, the dipstick figures indicated a total of about 62L. I knew the sight tubes were unreliable, but I thought the dipstick readings were a bit more accurate than this. Anyone else found this?
Sandie

CTSW FUEL TANKS

We did an experiment to measure fuel flow from the gascolator on the ground, clamping the hose from each tank in return, and got plenty more than the Spec flow from each tank. I was told by an experienced CT instructor not to worry, it is well known that CTSWs drain preferentially from the LH tank and that although level in sight tubes (assuming flying in balance) may even indicated zero in the LH tank he has never known a fuel feed failure in this situation. However, I never plan to fly it with the sight tube empty and if it does get that far, just lift that (LH) wing briefly to check that there is some fuel in the sight tube!

Another "experienced in the CT" concurs, and says he thinks the uneven flow is caused by lower pressure over the RH wing cap/vent than the LH. He is trialling a modification to the fuel return from the carb feed tee to route it, instead of back to the gascolator, back up the screen pillar to the port tank. He's hoping that it will also reduce the incidence of fuel vapour lock in very hot weather. I experienced this vapour lock with an instructor at about 200' at full throttle, on about the 8th take off on a hot 25C day. We had a slight loss of power and misfire, remedied by closing the throttle a bit.

No I haven't measured the quantity of fuel by draining it. I don't use the sight tubes to estimate fuel quantity, I dipstick each tank before every flight and stick that number into the Dynon. It seems to work.